function normalize (strArray) {
    const resultArray = [];
    if (strArray.length === 0) { return ''; }

    // Filter out any empty string values.
    strArray = strArray.filter((part) => part !== '');

    if (typeof strArray[0] !== 'string') {
        throw new TypeError('Url must be a string. Received ' + strArray[0]);
    }

    // If the first part is a plain protocol, we combine it with the next part.
    if (strArray[0].match(/^[^/:]+:\/*$/) && strArray.length > 1) {
        strArray[0] = strArray.shift() + strArray[0];
    }

    // If the first part is a leading slash, we combine it with the next part.
    if (strArray[0] === '/' && strArray.length > 1) {
        strArray[0] = strArray.shift() + strArray[0];
    }

    // There must be two or three slashes in the file protocol, two slashes in anything else.
    if (strArray[0].match(/^file:\/\/\//)) {
        strArray[0] = strArray[0].replace(/^([^/:]+):\/*/, '$1:///');
    } else if (!strArray[0].match(/^\[.*:.*\]/)) {
        // If the first part is not an IPv6 host, we replace the protocol.
        strArray[0] = strArray[0].replace(/^([^/:]+):\/*/, '$1://');
    }

    for (let i = 0; i < strArray.length; i++) {
        let component = strArray[i];

        if (typeof component !== 'string') {
            throw new TypeError('Url must be a string. Received ' + component);
        }

        if (i > 0) {
            // Removing the starting slashes for each component but the first.
            component = component.replace(/^[\/]+/, '');
        }
        if (i < strArray.length - 1) {
            // Removing the ending slashes for each component but the last.
            component = component.replace(/[\/]+$/, '');
        } else {
            // For the last component we will combine multiple slashes to a single one.
            component = component.replace(/[\/]+$/, '/');
        }

        if (component === '') { continue; }

        resultArray.push(component);
    }

    let str = '';

    for (let i = 0; i < resultArray.length; i++) {
        const part = resultArray[i];

        // Do not add a slash if this is the first part.
        if (i === 0) {
            str += part;
            continue;
        }

        const prevPart = resultArray[i - 1]

        // Do not add a slash if the previous part ends with start of the query param or hash.
        if (prevPart && prevPart.endsWith('?') || prevPart.endsWith('#')) {
            str += part;
            continue;
        }

        str += '/' + part;
    }
    // Each input component is now separated by a single slash except the possible first plain protocol part.

    // remove trailing slash before parameters or hash
    str = str.replace(/\/(\?|&|#[^!])/g, '$1');

    // replace ? and & in parameters with &
    const [beforeHash, afterHash] = str.split('#');
    const parts = beforeHash.split(/(?:\?|&)+/).filter(Boolean);
    str = parts.shift() + (parts.length > 0 ? '?': '') + parts.join('&') + (afterHash && afterHash.length > 0 ? '#' + afterHash : '');

    return str;
}

export default function urlJoin(...args) {
    const parts = Array.from(Array.isArray(args[0]) ? args[0] : args);
    return normalize(parts);
}